Drilling of earth formations by extrusion



1963 J. w. GRAHAM ETAL 3,078,934

DRILLING OF EARTH FORMATIONS BY EXTRUSION Filed May 15, 1959 2 Sheets-Sheet l FIG. I.

ATTORNE Feb. 26, 1963 Filed May 13, 1959 J. W. GRAHAM ETAL DRILLING OF EARTH FORMATIONS BY EXTRUSION INVENTO N w. 6 AM, N R NSON,JR.,

2 Sheets-Sheet 2 United States Patent Patented Feb. 26, 1963 3,078,934 DRILLING UF EARTH FORMATHQNS BY EXTRUSISN John W. Graham, Bellaire, and Leon H. Robinson, in, Houston, Tex., assignors, by mesne assignments, to jersey Production Research Company, Tulsa, Skin, a corporation of Delaware Filed May 13, E59, Ser. No. 312,8t24 6 Claims. (6i. 175-331) The present invention is directed to a drill bit. More particularly, the invention is concerned with drilling a well in which increased drilling rates are obtained. In its more specific aspects, the invention is concerned with an improved drill bit and method for drilling a well.

In drilling of wells, it is believed that the stress distribution within the rock is in part responsible for the slow drilling which is frequently encountered. The rock may be tectonically relaxed in a particular area of interest and thus the principal stresses within the rock may be equal. However, if a hole is drilled through this area, the hole will create discontinuities and stresses, particularly at or near the bottom of the hole. For example, the outer edge of the borehole may be under considerable compression because of the discontinuity caused by the presence of the hole. Moreover, the greater the sharpness of the corners (that is, the smaller the radius of the curvature), the greater will be the compressional stresses around the periphery of the hole. Stresses that are superimposed over the stress of the rock are those created by hydrostatic pressure of the fluid in the borehole, the overburden pressure caused by the weight of the formation, and the fluid pressure in the pores of the formation.

In areas where the subsurface rock fails malleably while drilling, an ideal situation would make full use of the compressional stresses existing at the bottom of the borehole. The drill bits employed in the art, however, do not take advantage of the stresses created by the borehole. It is therefore a feature of the present invention not only to exploit the stresses in existence but also to generate additional stresses within the rock which will increase drilling rates. This is done by imposing pressure on the earth formation pierced by the well at a plurality of spaced-apart points and extruding a portion of the formation from the bottom of the well through the drill bit at a plurality of points within the periphery of each of said plurality of points where the pressure is imposed.

This may be accomplished in a number of ways and, therefore, the invention will be further described by reference to the drawings in which:

FIG. 1 is a sectional view of a bit tooth of a preferred embodiment of the present invention in contact with the bottom of a well;

FIG. 2 is a view of a modified drill bit in accordance with FIG. 1 of the present invention;

FIG. 2a is a fragmentary sectional view of the band of FIG. 2;

FIG. 3 is a further modification of the device of FIG. 2;

FIG. 3a is sectional view of the elephant foot teeth of the device of PEG. 3;

FIG 4 illustrates a bit embodying the present invention;

FIG. 4a is a partial sectional view of FIG. 4;

FIG. 5 is a still further modification of the present invention; and

FIG. 5a is a bottom view of the device of FIG. 5.

Referring now to the drawing and particularly to FIG. 1, numeral 11 designates the wall of a well drilled from the earths surface, not shown, and having a drill bit 12 carried on the lower end of a drill string, not shown, contacting the bottom 13 of the well with the tooth 14, which is provided with a tapered passageway 15 drilled through the tooth and opening into the well. These holes 15 may be from /8 to inch in diameter and may be arranged in the outer ring of teeth on each cone of a hard rock bit. When the tooth 14 contacts the formation and begins to destroy the formation immediately below the bit 12, a portion of the formation is extruded through the passageway 15 and discharges into the annulus 16 and then is removed from the well with the drilling fluid. As the tooth continues its journey, the extruded rock removed from the region B in the bottom of the well 13 leaves a small hole below the zone of the destruction normally produced by the bit. This small hole produces stresses in the rock because of the discontinuity of the bottom of the hole just as the discontinuity produced by the borehole 11 induces compressional stresses around the periphery of the borehole. Accordingly, destruction of the rock is increased immediately surrounding the region B from which the rock is extruded, and therefore increased drilling rates are obtained.

In ordinary drilling operations, the solid bit teeth of conventional bits cause regions A surrounding each tooth to fail by brittleness and thus small rock chips are created therein. No advantage is taken of the tremendous malleability existing immediately below each bit tooth. The improved bit and method of drilling with the passage- Way 15 in the bit tooth 14 allows the rock to deform malleably through the tooth and hence is removed permanently from region B.

In FIG. 2, a modified bit it} having a body 21 has a plurality of roller cutters 22 rotatably mounted on the body 21. In the improved bit 20 of the present invention, the cone-shaped roller 22 has a band 23 on the outer edge of each of the cones provided with a plurality of open-ended passageways 24 tapering to a larger opening 25 immediately above the teeth 26 which are adjacent the apex of the cone. The holes 24 are suitably placed in the center of the band and are tapered with the smaller opening on the side of the band which contacts the bottom of the well, as shown in FIG. 2:1. It is considered that, in the practice of the present invention, the teeth 26 may also be provided with passageways which allow rock to be extruded therethrough.

Referring now to FIG. 3 which shows a modification of FIG. 2, the band 23 is provided with a plurality of heavy teeth 27 shaped like an elephants foot and formed with a plurality of open-ended passageways 28. These teeth have a large bearing surface and may be provided with a plurality of the tapered holes 28, as shown in FIG. 3a. As a modification of FIG. 3, all of the teeth of the device of FIG. 3 may be of the elephant foot type.

As a further modification of the present invention, a body member 39 in FIG. 4, which suitably may be a drill collar attached to a drill string, is provided with a plurality of mud ports 31 for circulation of drill fluid and has a spindle 32 rigidly attached thereto on which is rotatably mounted a sphere 33 provided with a plurality of open-ended passageways 34 which are tapered. As shown in FIG. 4a, the spindle 32 is arranged in a sleeve bearing 33a which makes a press fit in a recess in sphere 33 designed to receive the sleeve bearing 33a. Split rings 35 are urged into split ring groove 32a on spindle 32 and into split ring groove 36 in sleeve bearing 33a, thus making a connection between the sphere 33 and the spindle 32. In drilling with the device of FIGS. 4 and 4a, the sphere 33 by virtue of its eccentric arrangement on the spindle 32 revolves off-center around the spindle 32 and the rock is extruded through the passageways 34 and carried up the hole with the drilling fluid.

As a still further modification of the present invention, as shown in FIGS. 5 and 5a, a body member such as 40 3 provided with mud ports 41 has formed thereon a plurality of spikes 42, each of which has an open-ended passageway 43 terminating at the bottom of the spike and discharging within the cavity 44 which, in turn, discharges into the well through ports 41. The spikes 42 may be constructed of tungsten carbide and may also have diamonds mounted on the periphery of the spikes 42 such that when the improved device 40 is rotated and reciprocated, a scratching orchurning action accompanies the extrusion action of the rock through the passageways 43.

The present invention is quite advantageous and useful in that by imposing pressure on the rock, it becomes malleable and is caused to be extruded, creating additional stresses within the rock being drilled and thus contributing to improved drilling operations.

The invention will be further described by reference to the following operation in which water-saturated Carthage marble was subjected to a confining pressure of 10,000 -p.s.i. A tubular member having a /8 inch opening next to its face compressed the confined marble about 0.25 ,inch. The marble yielded and deformed malleably which caused it to extrude into the opening.

By confining pressure is meant normally the overburden pressure on the formation where the pressure is applied uniformly in all directions and ordinarily is the pressure on the rock surrounding the well bore. In the foregoing instance, the confining pressure simulated the confining pressure on the earth formation.

In practicing the invention, the malleablestate occurs .when the confining pressure is greater than the pore pressure of the rock by an amount in the range from about 2500 to about 5000 p,s.i., which may occur in wells at depths from about 5000 to about 10,000 feet.

The nature and objects of the present invention having been completely described and illustrated, what we wish to claim as new and useful and secure by Letters .Patent 1. A drill bit for drilling a well which comprises a body member, a drill member mounted on said body body member, a rotatable drill member mounted on said body member for contacting an earth formation, said drill member being formed to provide a plurality of open ended passageways, said drill member being adapted to contact said earth formation peripherally of one of the ends of each of said passageways in drilling of said well and the other end of each of said passageways discharging into the well whereby said earth formation is extruded adjacent the apex of the cone, and said drill member being adapted to contact said earth formation peripherally of one of the ends of each of said passageways openings on said band in drilling of said well and the other end of each of said passageways discharging into the well below said band adjacent said teeth whereby said earth formation is extruded through each of said passageways in contact with said earth formation.

6. ,A drill bit for drilling a well which comprises a body member, a drill member mounted on said body member for contacting an earth formation, said drill member beirig formed to provide a pluralityof tapered open-ended passageways, said drill member being adapted to contact said earth formation peripherally of one of the ends of said passageways in drilling of said well, each of said passageways discharging into the Well whereby said earth formation is extruded through each of said passageways in contact with said earth formation.

References Cited in'the file of this patent UNITED STATES PATENTS 371,679 Githens Oct. 18, 1887 474,297 Hotfmann May 3, 1892 479,041 Weller July 19, 1893 494,877 Miller Apr. 4, 1893 1,182,533 Double May 9, 1916 1,254,267 "Pickin Jan. 22, 1918 1,867,024 Oliver July 12, 1932 1,882,906 Renter Oct. 18, 1932 2,648,524 Dionisotti Aug. 11, 1953 2,840,348 Tilden June 24, 1958 

3. A DRILL BIT FOR DRILLING A WELL WHICH COMPRISES A BODY MEMBER, A ROTATABLE DRILL MEMBER MOUNTED ON SAID BODY MEMBER FOR CONTACTING AN EARTH FORMATION, SAID DRILL MEMBER BEING FORMED TO PROVIDE A PLURALITY OF OPENENDED PASSAGEWAYS, SAID DRILL MEMBER BEING ADAPTED TO CONTACT SAID EARTH FORMATION PERIPHERALLY OF ONE OF THE ENDS OF EACH OF SAID PASSAGEWAYS IN DRILLING OF SAID WELL AND THE OTHER END OF EACH OF SAID PASSAGEWAYS DISCHARGING INTO THE WELL WHEREBY SAID EARTH FORMATION IS EXTRUDED THROUGH EACH OF SAID PASSAGEWAYS IN CONTACT WITH SAID EARTH FORMATION. 